The objective of this grant proposal is to develop a noninvasive method to implant polymers using photopolymerization. This allows solid hydrogels to be implanted without surgical intervention. Enough light is able to penetrate tissue, including skin, to trigger the photopolymerization of an injected liquid, polymer solution to a solid hydrogel. Further study of transdermal photopolymerization using alternative photoinitiating systems and wavelengths of light is proposed in order to increase depths at which implants can be photopolymerized. Photopolymerization will be applied to the tissue engineering of cartilage. Cartilage lacks the ability to regenerate and its loss by trauma, congenital abnormalities or tumors gives few options to the physician for replacement. Preliminary data has shown that chondrocytes survive encapsulation, injection and photopolymerization to form neocartilage. Important biological factors, including growth factors and adhesion peptides, will be incorporated into photopolymerizing hydrogels to determine if they can accelerate cartilage development and produce cartilage with biochemical and biomechanical properties similar to native cartilage. The tissue engineering of cartilage will be examined both in vitro and in vivo, in particular in an immune competent animal. The integration of photopolymerized tissue engineered cell/polymer implants with surrounding native cartilage is critical to the clinical application of tissue engineered cartilage and will be addressed. In conclusion, this proposal addresses methods for noninvasive polymer implantation, which applied to cartilage tissue engineering, would provide physicians with a significant alternative to cartilage replacement for craniofacial reconstruction and orthopedic surgery. The specific goals of this proposal include: (1) development of a highly efficient, biocompatible transdermal or transtissue photopolymerization system for noninvasive polymer implantation; (2) development of an injectable tissue engineered cartilage using transdermal photopolymerization; (3) increase cellular biocompatibility of the polymer hydrogel through the incorporation of bioactive peptides and proteins; and (4) integration of tissue engineered and native cartilage for the correction of cartilage defects.